As one of the conventional vehicles each having the internal combustion engine mounted thereon, there has been known the vehicle having the internal combustion engine and the continuously variable transmission mounted thereon to continuously change a power of the internal combustion engine to be transmitted to drive wheels. The vehicle having the continuously variable transmission is equipped with a control apparatus for controlling torque generated by the internal combustion engine and a speed change ratio of the continuously variable transmission to secure an optimum fuel consumption of the vehicle. The control apparatus is adapted to determine a target torque of the internal combustion engine in accordance with an accelerator opening degree and the vehicle speed in response to the operation of an accelerator pedal by a driver.
The control apparatus is constructed to have an engine rotational speed and the torque of the internal combustion engine associated with a requested driving force, and to memorize a fuel consumption map set with an optimum fuel consumption line associated with the engine rotational speed and the torque. The control apparatus is constructed to control the internal combustion engine and the continuously variable transmission to have an operation point represented by the engine rotational speed and the torque of the internal combustion engine moved to the requested driving force on the optimum fuel consumption line.
As one of these control apparatuses of the vehicles, there has been known the control apparatus which can maintain the engine rotational speed at a constant level to suppress bad feelings to the driver by controlling the internal combustion engine and the continuously variable transmission to have the operation point moved on the line different from the optimum fuel consumption line when the target operation point of the internal combustion engine is moved in response to the operation of the accelerator pedal by the driver in the case that a current operation point of the internal combustion engine in the fuel consumption map is on the optimum fuel consumption line (for example see Patent Document 1).
The control apparatus of the vehicle disclosed in the Patent Document 1 is adapted to determine whether or not the target operation point is within a predetermined width area with the optimum fuel consumption line formed therein as a center line when the target operation point is moved by the variation of the accelerator opening degree in the state in which the operation point is on the optimum fuel consumption line.
When the control apparatus determines that the target operation point is within the predetermined width area with the optimum fuel consumption line formed therein as the center line, the operation point is moved on the constant engine rotational speed line different from the optimum fuel consumption line, thereby causing only the torque to be varied with no variation of the engine rotational speed. The control apparatus is adapted to have the operation point moved to the optimum fuel consumption line for a predetermined period of time.
For this reason, the control apparatus of the vehicle disclosed in the Patent Document 1 is adapted to match the driving force with a target driving force without varying the engine rotational speed of the internal combustion engine, thereby preventing the bad feelings caused by the variation of the engine rotational speed to the driver.
Incidentally, the control apparatus of the vehicle provided with the continuously variable transmission including the control apparatus of the vehicle disclosed in the Patent Document 1 is generally adapted to control the internal combustion engine and the continuously variable transmission to have the operation point moved along the optimum fuel consumption line in the above fuel consumption map as much as possible, thereby reducing a fuel consumption amount of the internal combustion engine to improve the fuel consumption.